The scientific method

The science of biology

Video transcript

Let's explore the scientific method. Which at first might seem a bit intimidating, but when we walk through it, you'll see that it's actually almost a common-sense way of looking at the world and making progress in our understanding of the
world and feeling good about that progress of our understanding of the world. So, let's just use a tangible example here, and we'll walk through what we could consider the steps of the scientific method, and you'll see different steps articulated in different
ways, but they all boil down to the same thing. You observe something
about reality, and you say, well, let me try to come up with a reason for why that observation happens, and then you try
to test that explanation. It's very important that you come up with explanations that you
can test, and then you can see if they're true, and then based on whether they're true, you keep iterating. If it's not true, you come
up with another explanation. If it is true, but it
doesn't explain everything, well once again, you try
to explain more of it. So, as a tangible example,
let's say that you live in, in I don't know, northern
Canada or something, and let's say that you live near
the beach, but there's also a pond near your
house, and you notice that the pond, it tends to
freeze over sooner in the Winter than the ocean does. It does that faster and
even does it at higher temperatures than when the ocean seems to freeze over. So, you could view that
as your observation. So, the first step is you're
making an observation. Observation. In our particular case
is that the pond freezes over at higher temperatures than the ocean does, and it freezes over
sooner in the Winter. Well, the next question that you might wanna, or the next step you could view as a scientific method. It doesn't have to be
this regimented, but this is a structured way of thinking about it. Well, ask yourself a question. Ask a question. Why does, so in this
particular question, or in this particular scenario,
why does the pond tend to freeze over faster and
at higher temperatures than the ocean does? Well, you then try to answer
that question, and this is a key part of the scientific method, is what you do in this third step, is that you try to create
an explanation, but what's key is that it is a testable explanation. So, you try to create a testable explanation. Testable explanation,
and this is kind of the core, one of the core
pillars of the scientific method, and this testable
explanation is called your hypothesis. Your hypothesis. And so, in this particular
case, a testable explanation could be
that, well the ocean is made up of salt water, and this pond is fresh water, so your testable explanation could be salt water, salt water has lower freezing point. Has lower freezing, freezing point. Lower freezing point, so it takes colder temperatures to freeze
it than fresh water. Than fresh water. So, this, right over here, this would be a good hypothesis. It doesn't matter
whether the hypothesis is actually true or not. We haven't actually run
the experiment, but it's a good one, because we can construct an experiment that tests this very well. Now, what would be an example of a bad hypothesis or of something
that you couldn't even necessarily consider as part of the scientific method? Well, you could say that there is a fairy that blesses that blesses, let's say that performs magic, performs magic on the pond to freeze it faster. Freeze it faster. And, the reason why this
isn't so good is that this is not so testable,
because it's depending on this fairy, and you
don't know how to convince the fairy to try to do it again. You haven't seen the fairy. You haven't observed the fairy. It's not based on any observation, and so this one right over here, this would not be a good hypothesis for the scientific method, so we would
wanna rule that one out. So, let's go back to our
testable explanation, our hypothesis. Salt water has a lower freezing
point than fresh water. Well, the next step would be to make a prediction based
on that, and this is the part where we're really
designing an experiment. So, you could just view
all of this as designing. Let me do this in a different color. Where we wanna design an experiment. Design an experiment. And in that experiments
lets say, and let's see, the next two steps I will put as part of this experimental. Whoops. I messed up. Let me, I did my undo step. So, the next part that I
will do is the experiment. Experiment. And there you go. So, the first thing is,
we'll say I take, you know, there's all sorts of things
that are going on outside. The ocean has waves. You know, maybe there are boats going by that might potentially break up the ice. So, I just wanna isolate
that one variable that I care about, whether something is salt water or not, and I want a control for everything else. So, I want a control for whether there's waves or not or whether
there's wind or any other possible explanation for why the pond freezes over faster. So, what I do, in a very
controlled environment I take two cups. I take two cups. That's one cup and two cups, and I put water in those cups. I put water in those cups. Now, let's say I start with
distilled water, but then this one stays, the
first one right over here stays distilled, and
distilled means that through evaporation I've taken
out all of the impurities of that water, and in the second one I take that distilled
water, and I throw a bunch of salt in it. So, this one is fresh,
very fresh, and in fact, far fresher than you would find in a pond. It's distilled water. And then this is over
here, this is salt water. So, you wouldn't see the
salt, but just for our visuals, you depict it. Then we would make a prediction, and we could even view this as step 4, our prediction. We predict that the fresh
water will freeze at a higher temperature than the salt water. So, our prediction,
let's say the fresh freezes at zero degrees Celsius, but salt doesn't. Salt water doesn't. Salt water doesn't. So, what you then do is that
you test your prediction. So, then you test it. And how would you test it? Well, you could have a
very accurate freezer that is exactly at zero degrees
Celsius, and you put both of these cups into
it, and you wanna make sure that they're identical
and everything where you control for everything else. You control for the surface area. You control for the material of the glass. You control for how much water there is. But, then you test it. Then you see what happened from your test. Leave it in overnight,
and if you see that the fresh water has frozen
over, so it's frozen over, but the salt water
hasn't, well then that seems to validate your
testable explanation. That salt water has a
lower freezing point than fresh water, and if it didn't
freeze, well it's like, okay, well maybe that, or if
there isn't a difference, maybe either both of them
didn't freeze or both of them did freeze, then
you might say, well, okay, that wasn't a good explanation. I have to find another explanation for why the ocean seems to freeze
at a lower temperature. Or, you might say, well that's part of the explanation, but that by itself doesn't explain it, or you
might now wanna ask even further questions about, well, when does salt water freeze, and what
else is it dependent on? Do the waves have an impact? Does the wind have an impact? So, then you can go into the process of iterating and refining. So, you then refine, refine, refine and iterate on the process. When I'm talking about iterate, you're doing it over again, but then, based on the things that you've learned. So, you might come up with a more refined testable explanation, or you might come up with more experiments that could get you a better understanding of the difference between fresh and salt water, or you might try to come up with experiments for why exactly, what is it
about the salt that makes this water harder to freeze? So, that's essentially the essence of the scientific method,
and I wanna emphasize this isn't some, you know, bizarre thing. This is logical reasoning. Make a testable explanation for something that you're observing
in the world, and then you test it, and you
see if your explanation seems to hold up based
on the data from your test. And then whether or not it holds up, you then keep going, and
you keep refining. And you keep learning more
about the world, and the reason why this is better
than just saying, oh well, look, okay, I see the pond
has frozen over and the ocean hasn't, it must be the
salt water, and you know, I just feel good about
that, is that you can't feel good about that. There's a million
different reasons, and you shouldn't just go on
your gut, 'cause at some point, your gut might be right 90% of the time, but that 10%
that it's wrong, you're going to be passing on
knowledge or assumptions about the world that
aren't true, and then other people are going to build
on that, and then all of our knowledge is going
to be built on kind of a shaky foundation, and
so the scientific method ensures that our foundation is strong. And I'll leave you with
the gentleman who's often considered to be the father, or one of the fathers of the scientific method. He lived in Cairo, and in what is now Egypt, nearly 1,000 or roughly
1,000 years ago. And he was a famous astronomer and
phycisist and mathematician. And his quote is a pretty
powerful one, 'cause I think it even stands today: "The duty of the man who
investigates the writings of scientists, if learning
the truth is his goal, ..." Let me start over, just
so I can get the dramatic effect right. "The duty of the man who
investigates the writings of scientists, if learning
the truth is his goal, is to make himself an enemy of all that he reads, and ... attack it from every side. He should also suspect
himself as he performs his critical examination
of it, so that he may avoid falling into either
prejudice or leniency." Hasan Ibn al-Haytham,
and his Latinized name is Alhazen. So, he's saying be skeptical,
and not just skeptical of what other people
write and read, but even of yourself. And another
aspect of the scientific method which is super
important is, if someone says they made a hypothesis
and they tested and they got a result, in order for
that to be a good test and in order for that to be a good
hypothesis, that experiment has to be reproducible. Someone can't say, oh it's
only, you know, a certain time that only happens once
every 100 years and not, that that's why it happened that day. It has to be reproducible,
and reproducible is key, because then
another skeptical scientist like yourself can say, let me see if I can reproduce it. Let me not just believe
it, because that person looks like they're
smart, and they said that it is true.